Inter-proton distances derived from NOE (nuclear Overhauser effect) data are the main structural information obtained from NMR. The focus of my research is to obtain accurate distance constraints from NOE data using complete relaxation matrix method. It has been shown that for high resolution structure determination, it is important that accurate distance constraints are used in the structure calculations. This is particularly true for DNA, DNA-drug complex and RNA, where the number of NMR distance constraints per residue is relatively small. We have developed programs CORMA and MARDIGRAS for the analysis of NOE data using complete relaxation matrix methods. Accurate distance constraints can be obtained by taking into account indirect cross relaxation (spin diffusion) in large spin systems. Distance restraints are determined by adding random errors to NOE intensities using RANDMARDI procedure. Recent development of CORMA and MARDIGRAS involves rewriting the Fortran code in C++, and the interface with Sparky, a graphical NMR software used for display and assignment of multi-dimensional NMR spectra.